Research On Detection Methods For Determination Of Free Fatty Acids In Edible Oils

Free fatty acids(FFA)content(acid value)is an important edible fats health indicators,further degradation of the aldehyde,ketone,acid will destroy the fat-soluble vitamins,that has effect on human health.Currently,the determination of domestic edible oil FFA are:acid-base titration,colorimetry,potentiometric titration,voltammetry,and near infrared spectroscopy and so on,the acid-base titration method in the national standard GB/T 5530-2005 is the mainly one,but there are the problems such as vulnerable to sample,standard solution,indicators and low sensitivity and accuracy.In infrared detection,it need to use a narrow flow cell,but the high viscosity oils at room temperature is difficult to put a narrow flow cell,and is difficult to clean,easy to cause cross-contamination between samples and other issues.A method that using PE films collection spectra can effectively avoid the problems above.In order to improve the detection accuracy of free fatty acids,some using potassium phthalimide and the free fatty acids in the frying oil by the reaction of phthalimide,to establish the spectrum of UV-based edible oil FFA measurement method,but the model for detecting the frying oil can limit their widespread use.In this study,this new method of spectral acquisition and Fourier transform infrared spectroscopy(FTIR)combined to form a new measuring method,while taking advantage of phthalimide potassium and free fatty acids in edible oils react phthalic dicarboximide-based edible oil FFA create UV spectrum measurement method.(1)Using the same kind of oil sample spectrum and FFA free spectral subtraction process eliminates the edible substrate effect,spectral absorbance values obtained in the characteristic absorption peak of the FFA and the FFA only related to the content of edible oil FFA create a test model.Blind validation samples and samples with different levels of FFA model was validated with national standard method were compared.The results show that:the model predicted values obtained with the titration results are very close to the value of the correlation coefficient(R)were greater than 0.99,indicating a good model to predict the effect of the type of fat and is not affected,can be used for quantitative analysis of FFA.(2)In order to further simplify the measurement process,the use of FFA characteristic absorption correction model to establish the basis of the correlation peak at the peak of its first multiplier effect of the elimination of the base,using an improved method of coating method combined with the calibration model,the establishment of edible oil FFA determination model.Blind validation samples and samples with different levels of FFA model was validated with national standard method were compared.The results show that:the model predicted values obtained with the titration results are very close to the value of the correlation coefficient(R)were greater than 0.99,indicating a good model to predict the effect of the type of fat and is not affected;model to predict the relative error of 0.25%?7.58%,relative standard deviation(RSD)was 1.29%,indicating that the model has high accuracy and precision.Indicates that the model can predict the effect instead of the national standard method for quantitative analysis of FFA,the operation easier.(3)FFA is reacted with potassium phthalimide to generate quantitative phthalimide,phthalimide using a characteristic absorption peak in the UV spectrum principles of 290nm wavelength,detecting create edible FFA models with different levels of FFA and blind sample validation samples to validate the model were compared with titration analysis.The results show that:the model predicted values obtained with the titration results are very close to the value of the correlation coefficient(R)were greater than 0.99,indicating a good model to predict the effect of the type of fat and is not affected;model to predict the relative error in the range of 0.22%?6.87%,relative standard deviation(RSD)was 1.34%,indicating that the model has high accuracy and precision.Detection by UV spectroscopy of edible FFA is feasible.